(1) Field of the Invention
The present invention relates to water-in-oil (W/O) emulsion explosive compositions having excellent stability in storage, detonability at low temperature, explosion reactivity and sympathetic detonability, which is obtained by the use of at least one of specifically limited sulfonates as an emulsifier.
(2) Description of the Prior Art
Heretofore, the improvement of explosion reactivity (usually represented by the explosion velocity) in general explosives has been effected by (1) selecting the components of the explosive composition and (2) varying the mixed state between each component of the explosive composition. The above described former method (1) comprises selecting substances having a high reaction velocity, selecting substances which generate a large heat energy upon the reaction, that is, have a high explosion heat, and the like, as a means for enhancing the reactivity of explosive composition. The above described latter method (2) comprises contacting an oxidizer with a fuel in fine particle form, that is, increasing the contact area or dissolving these substances with each other through water to increase the contact area, as a means for enhancing the reactivity of mixed phase.
When a water soluble substance and a water insoluble substance are contained in a slurry explosive, it is very difficult to contact both the substances in a dissolution state through water, so that it is necessary to form a mixed phase wherein an aqueous solution of a water soluble substance and a water insoluble substance are contacted with each other in the state where both the substances are formed into particle state to increase the contact area.
Almost all of conventional slurry explosive compositions have been oil-in-water (referred to as O/W hereinafter) emulsion explosive compositions, in which water of the major component envelops water insoluble substances or water soluble substances which can not be fully dissolved in water and remain in water. The major part of the water soluble substances in the O/W emulsion explosive compositions are oxidizers, for example, inorganic oxidizer salts, such as ammonium nitrate and the like, and the major part of the water insoluble substances are fuels or sensitizers which act as a fuel together, for example, aluminum, nitromethane and the like.
In general, in slurry explosive compositions, when the components are classified into water insoluble substances (referred to as "O") and water soluble substances (referred to as "W"), the compounding ratio by weight of O/W is generally not more than 25/75. Thus, when it is considered that the dispersed particle size in O/W emulsion and W/O emulsion is equal, the contact area of O and W is larger in W/O emulsion, wherein O which is smaller in the amount envelops W which is larger in the amount, than in O/W emulsion. Accordingly, it is expected that the explosion reactivity is improved in W/O emulsion. As the results, the explosive wherein smoke is few and the after-detonation fume is good, can be obtained.
Thus, in view of increase of the contact area, a variety of W/O emulsion explosive compositions have been disclosed instead of the prior O/W emulsion explosive compositions in U.S. Pat. Nos. 3,161,551; 3,164,503; 3,212,945; 3,356,547; 3,442,727; 3,447,978; 3,617,406; 3,674,578; 3,765,964; 3,770,522 and 4,008,108. In these W/O emulsion explosive compositions, the quality of W/O emulsion explosive compositions is greatly influenced by the kind of emulsifier necessary for forming W/O emulsion. In the W/O emulsion explosive compositions described in the above described United States Patent specifications, emulsifiers shown in the following Table 1 are used.
TABLE 1 ______________________________________ U.S. Pat. No. Emulsifier ______________________________________ 3,161,551 (1) 4,4-bis(hydroxymethyl)-1- pentadecyl-2-oxazoline (2) 4-methyl-4-hydroxymethyl- 1-heptadecyl-2-oxazoline 3,212,945 (1) glycerine monostearate (2) alkyl ester of abietic acid and metal salt thereof (3) polyglycol ether (4) addition product of higher fatty acid amine to ethylene oxide (5) polyvinyl alcohol (6) ester of higher fatty acid with higher alcohol (7) salt of higher fatty acid 3,442,727 alkyl phosphoric acid ester 3,164,503 3,447,978 sorbitan fatty acid ester 3,765,964 3,356,547 (1) calcium stearate (2) zinc stearate 3,770,522 (1) ammonium stearate (2) alkali metal salt of stearic acid 4,008,108 sodium stearate 3,617,406 (1) polyoxyethylene alkyl ester (2) polyoxyethylene alcohol (3) polyoxyethylene alkyl ether 3,674,578 (1) metal salt of oleic acid (2) sorbitan fatty acid ester (3) ethylene oxide condensate of fatty acid (4) dodecylbenzenesulfonic acid (5) tall oil amide ______________________________________
It is commonly known that the above described various emulsifiers are used, but almost all W/O emulsion explosive compositions using an emulsifier other than sorbitan fatty acid ester are poor in the emulsion stability in storage, and are insufficient in the explosion reactivity and in the detonability at low temperature. W/O emulsion explosive compositions using sorbitan fatty acid ester are good in the emulsion stability in storage, the explosion reactivity and the like. However, commercially available sorbitan fatty acid ester is not always composed of single component and often contains its isomers, polycondensate and the like. Therefore, it has been difficult to produce W/O emulsion explosive compositions having always stable performance by the use of commercially available sorbitan fatty acid ester.